import pandas as pd
import os

# ── Config ────────────────────────────────────────────────────────────────────
INPUT_FILE  = 'users_to_keep.csv'
OUTPUT_FILE = 'users_to_keep_clean.csv'
# ──────────────────────────────────────────────────────────────────────────────


def load_csv(filepath: str) -> pd.DataFrame:
    """Load CSV file and return a DataFrame."""
    if not os.path.exists(filepath):
        raise FileNotFoundError(f"File not found: {filepath}")
    return pd.read_csv(filepath)


def remove_duplicates(df: pd.DataFrame) -> pd.DataFrame:
    """Normalize handles and remove duplicate rows."""
    df['Handle'] = df['Handle'].str.strip().str.lower()
    return df.drop_duplicates(subset='Handle', keep='first')


def save_csv(df: pd.DataFrame, filepath: str) -> None:
    """Save DataFrame to CSV."""
    df.to_csv(filepath, index=False)


def print_report(before: int, after: int, output: str) -> None:
    """Print a summary report."""
    removed = before - after
    print("─" * 40)
    print(f"  Rows before : {before}")
    print(f"  Rows after  : {after}")
    print(f"  Removed     : {removed}")
    print(f"  Saved to    : {output}")
    print("─" * 40)


def main():
    print(f"\n📂 Loading '{INPUT_FILE}'...")
    df = load_csv(INPUT_FILE)
    before = len(df)

    print("🔍 Removing duplicates...")
    df_clean = remove_duplicates(df)
    after = len(df_clean)

    print(f"💾 Saving to '{OUTPUT_FILE}'...")
    save_csv(df_clean, OUTPUT_FILE)

    print_report(before, after, OUTPUT_FILE)
    print("✅ Done!\n")


if __name__ == '__main__':
    main()